Overshot



July 2, 1929- l J. c; sToKEs ET AL 1,719,144

' OVERSHOT Filed April 50, 1928 rammed July A2, 1929.l

yUNITED STATES JOHN C. STOKES, HOUSTON, TEXAS, AND FRANK C. GIGNOUX, OFLOS ANGELES, CALIFORNIA, ASSIGNORS TO REED ROLLER BIT COMPANY, FHOUSTON, TEXAS`A CORPORATION OF TEXAS.

, ovERsHoT.

Application filed April 3o,

This invention relates to overshots, and more particularly to overshotsof the type covered by Letters Patent of the United States No.1,442,188, toi John C. Stokes, of

January 16th, 1928.

The overshot disclosed by the said Letters Patent embodies a pair ofpivoteddogs attached to the end of a cable'and having teeth on the lowerend thereof to engage the conilocal head of a collapsible bit or thelike, the upper ends of said jaws remote from said teeth extendinglaterally to be engaged by a trip tube dropped thereon to swing theteeth but of engagement -with said conical head or l5 the like.

The laterally extending upper ends ofthe dogs just referred to quiteoften become caught on irregular internal surfaces of deep well drillstems and are either broken off or so badly worn that they no longerextend into the path of the trip tube and consequently the bit or otherelement held by the dogs cannot be released.

' This invention has for one of its specific objects the provision of'anew andfimproved overshot embodying dogs the upper ends of which do not'project laterally outside of the overshot body, and are therefore notsubjected to the danger of becoming worn or broken, the releasingmovement of the dogs being effected bymeans actuated by the trip tube.

Other objects of the invention will herein-v after appear.

In the accompanying drawings, which are illustrative of the preferredembodiment of the invention, Fig. 1 is a fragmentary side elevationpartly in section, of a drill stem with a bit therein, and the overshotgripping the conical head of the bit; Fig. 2, a view similar 40 to Fig.1 and showing the teeth of the dogs moved out of engagement with theconical l head by the trip tube; and Fig; 3, a View similar to Fig. 1and at a right angle thereto.

. The drill stem is shown at A, the bit at B, and the overshot at C. j

The bit comprises no part of the present invention, and is shown only toillustrate one use to which the overshot may be put. Ordinarily,collapsible bits are lowered into drill stems by means of the overshoton the end of n a cable. When the bit reaches the lower end of the stem,the overshot is disconnected by dropping a trip tube on the dogs, asabove pointed out,ra fter which it is removed, and

drilling commeucedf When removal of the bit becomes desirable, theovershot is again lowered into the stern and automatically becomesconnected to the bit.

Fig. 1 illustrates-the overshot connected'to the bit. It will beobserved that the teeth 1a of the dogs 1 are gripping the conical head 2of the bit.

In Fig. 2, the trip tube 10 has effected disengagement ofthe dogs andthe head of the bit by moving the upper ends of the dogs 1 inwardly bymeans of the arms 3 and springs 4. From this position, the overshot maybe moved vupwardly awayfrom the bit.

The dogs 1 do not extend outwardly from the overshot body 5 andtherefore cannot be .worn or broken bybecoming caught ori irregularitiesin the drill stem A.

The reduction of the upper end of the body 5 forms a shoulder 5'l tolimit the downward movement of the trip tube 10.

The cable 6 is suitably secured to the cap 1.5 which is screwed on theshank 5 of the body 5. The body is longitudinaly slotted as shown at 5for the reception of the dogs l, arlns 3, and springs 4; and it has arecess 5d in its bottom for the reception of the bit or other element tobe engaged by the dogs! A T-shaped plug 7 extends into a socket 5e inthe upper Wall of slot 5 and is held therein by setv screw 8. This plugsu pports the arms 3 which are pivoted at 9 in the lateral slotsthereof. The inner walls 7 L of the slots are any gular, as shown, sothat the arms 3 can swing outwardly only a limited distance, and cannot,therefore, become caught on obstacles in the drill stem. r

The plug 7 has also apair of diverging slots 7 b in which the springs 4are secured.

The springs 4 extend downwardly and outvardly into the pockets 1b in theupper ends of ogs 1. y

The dogs 1 are pivoted at 11 and have openings 1c through which the pin12 extends. The diameter of each opening 1c is much greater than thediameter of the pin 12, so the dogs 1 may swing only a limited amount ontheir pivot 11, and objectionable lateral projection thereof prevented'.l

The dogs 1 are normally in the position illustrated by Fig. 1, bothgravity and the springs 4 serving to urge the dogs into this position.The head 2 forces the dogs apart and become locked therebetween. Whenthe trip tube is ldropped onto the overshot, it moves the -arIns 3inwardly, the arms 3 moving the springs 4, and the springs 4 the upperends of the dogs l. Thus the teeth la of the dogsv are moved out ofengagement with the head 2.

It will be noted that all of the parts may quickly and easily beseparated, and so dogs of various sizes may successively be used withthe other parts.

The invention is not limited to the preferred elnbodiment shown andvarious changes may be made Without departing from, the scope of thefollowing claims.

l. An overshot having movable dogs, dogactuating arms, and springsconnecting said dogs and arms.

2. An overshot having movable dogs, spring means serving to normallyhold said dogs in an engaging position, and means, to actuate saidspring means to move said dogs into a releasing position.

3. ln` an overshot, a pair of dogs, each of said dogs having a pair ofopenings therein, a pivot pin extending through one of the openings ineach dog, and a stop pin extending through the other of the openings ineach dog, Said stop pin fitting loosely in the last-mentioned openings,whereby the pivoted movement of the dogs is limited.

4. An overshot having a body, dogs movably mountedon said body, and armsmovably mounted on said body above and operatively connected to saiddogs and adapted to be actuated by tripping means.

5. A'n overshot having a body with a slot therein, dogs movably mountedin saidl slot and arms movably mounted in said slot, extending laterallyto be engaged by tripping means, and operatively connected to said dogs.

6. An overshot having a body with a slot therein, dogs movably mountedin said slot, arms movably mounted in said slot and extending laterallyto be engaged by tripping means, and spring means in said slot andoperatively connecting said dogs and arms.

7.,An overshot having a body with a reduced upper portion, dogs movablymounted in the lower portion of said body, and arms movably mounted insaid reduced upper portion operatively connected to said dogs, andy insaid body between said arms, dogs connected to said springs and means toactuate said arms.

10. An overshot having a body,/dogs and arms movablymounted in saidbody, the outward movement of said dogs and arms being limited, saiddogs and arms being operatively .connected together, said arms beingadapted to be engaged by tripping means.

11. An oversliot having a body, aremovable plug in said body, armspivoted to said plug, springs carried .by said plug adjacent said arms,dogs removably mounted in said body and connected to said springs, andmeans to actuate said arms to move said dogs.

In testimony whereof, we hereunto afiix our signatures.

JOHN. C. STOKES. FRANK C. GIGNOUX.

